update pecl-http extension commit due to invalid commit reference

php-ext/http refuses to clone due to;

Cloning into 'php-ext/http'...
remote: Reusing existing pack: 7618, done.
remote: Total 7618 (delta 0), reused 0 (delta 0)
Receiving objects: 100% (7618/7618), 1.68 MiB | 637.00 KiB/s, done.
Resolving deltas: 100% (5793/5793), done.
Checking connectivity... done
fatal: reference is not a tree: 4f5c3c8b8b58ffc1ef0f70e3b347dfbb6b63fd0f

leaving the php-ext/http directory empty.